Political trends come and go in response to events. Gun control was the rage during the Clinton administration, but over the past decade or so it became an obsolete cause. After the horrific crimes in Newtown and Aurora, though, it's staging a comeback.

One thing hasn't changed: The agenda includes mostly measures that will have little or no effect on the problems they are supposed to address. They are Potemkin remedies — presentable facades with empty space behind them.

This is something that supporters as well as opponents labor to conceal. Treating them as serious allows them both to posture for their own advantage.

So on Wednesday, President Barack Obama unveiled a raft of executive actions and proposed changes in federal law intended to prevent mass shootings and chronic gun violence. A few are innocuous and reasonably promising, like improving databases for background checks and helping "ensure that young people get the mental health treatment they need."

But the most notable ones fall into three categories. In the category of "useless" is the ban on "assault weapons," which has been tried before with no evident effect. The administration is fond of demonizing a style of firearm that the gun industry likes to glamorize.

What they are talking about, though, are ordinary rifles tricked out and blinged up to resemble something else: military arms designed for the battlefield. The "weapons of war" Obama wants to ban do nothing that other, legal weapons won't do just as quickly and just as destructively.

Most criminals have no need of them. In 2011, reports The New York Times, 6,220 people were killed with handguns — compared to 323 by rifles of any kind, including "assault weapons."

In the "probably useless" realm is a ban on ammunition magazines holding more than 10 rounds, which was part of the 1994 assault weapons ban. A mass shooter can overcome the restriction by carrying multiple magazines or multiple guns — as many of them do anyway. The notion that an attacker can be subdued when he stops to reload works better in movies than in real life, where it is virtually unknown.

Enforcing a limit on magazine size may be harder than you think. Recently a company called Defense Distributed showed it could use a 3D printer to make a plastic 30-round magazine. "The Internet happened since the last assault weapons ban," founder Cody Wilson told Forbes. "This is a fledgling tech, but look at what we're able to do."

Both of the White House proposals would inconvenience law-abiding gun owners who use their firearms — including "assault weapons" with large magazines — entirely for innocent purposes, including hunting, target shooting and home defense. They would not impede violent criminals from obtaining guns, which are widely available in illegal markets and will remain abundant.

In the category of "possibly helpful" is a new rule requiring private gun sales to include a federal background check — as purchases from licensed dealers already do. That change, which would cover some 40 percent of all gun transactions, holds the potential of preventing convicted felons from getting guns by stopping them at the point of sale.

But don't expect too much. Supporters point to research indicating that 80 percent of criminals bought their guns privately. But as a rule, the people who sell guns to criminals are criminals, who do not make a fetish of complying with federal regulations. Most if not all of this commerce will continue.

The chief effect will be on law-abiding people who are accustomed to buying guns from friends and fellow enthusiasts. Maybe the added cost and trouble will pay off by disarming some career crooks and homicidal maniacs.

Same with Wade Michael Page, who killed six people at a Sikh temple near Milwaukee. Jacob Tyler Roberts, who killed two people on a spree in an Oregon shopping mall, wouldn't have been affected, since he got his gun by stealing it.

The mistakes Obama is making are familiar ones: exploiting misconceptions about guns, exaggerating the value of symbolic actions and presuming that new laws will foil incorrigible lawbreakers. The assault weapons ban was irrelevant to fighting crime before, which is no reason it can't be irrelevant again.

Steve Chapman is a member of the Tribune's editorial board and blogs at chicagotribune.com/chapman.

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